RubyMine 7.1.3 Help

Keymap:

Configuring Autofolding Behavior

RubyMine allows displaying source code in a folded form,
making it really concise, and hiding from view the details you might consider less important.
When a file is first opened for editing, certain code constructs can be shown folded.
It is up to you to define the desired set of code constructs to be folded by default.
When you hover your mouse pointer over the collapsed code fragment,
its preview is displayed in a pop-up window.